Skid control system including cycling and checking circuit for plural modulating valve

ABSTRACT

A skid control system including a first brake pressure modulating valve for the front wheels, a second brake pressure modulating valve for the rear wheels and an apparatus for automatically cycling and checking the valves independently of the skid control function in order to prevent deterioration of the valve from inaction. A cycling inhibit unit is provided so that cycling of at least one of the valves is inhibited when the brakes are applied by the vehicle operator whereby the braking pressure to all of the brakes will not be relieved.

United States Patent [191 Birge Mar. 12, 1974 [54] SKID CONTROL SYSTEM INCLUDING 3,680,923 8/1972 Peterson et al 303/21 AF CYCLING N CHECKING CIRCUIT FOR 3,516,715 6/1970 Fielek, Jr. et a1 303/21 AF PLURAL MODULATING VALVE Primary ExaminerDuane A. Reger Assistant Examiner-Stephen G. Kunin Attorney, Agent, or FirmHarness,Dickey 8L Pierce 5 7 ABSTRACT A skid control system including a first brake pressure modulating valve for the front wheels, a second brake pressure modulating valve for the rear wheels and an apparatus for automatically cycling and checking the valves independently of the skid control function in order to prevent deterioration of the valve from inaction. A cycling inhibit unit is provided so that cycling of at least one of the valves is inhibited when the brakes are applied by the vehicle operator whereby the braking pressure to all of the brakes will not be relieved.

26 Claims, 1 Drawing Figure SKID CONTROL SYSTEM INCLUDING CYCLING AND CHECKING CIRCUIT FOR PLURAL MODULATING VALVE SUMMARY BACKGROUND OF THE INVENTION The present invention relates to a skid control system having a circuit for cycling and checking at least two modulating valves of the skid control system. A related system appears in the patent to Fielek, Jr., et al. No. 3,516,715 entitled Skid Control System Including Valve Cycling and Checking Circuit issued June 23, 1970, and assigned to the same assignee as the assignee of this application, the teachings of which are incorporated herein by reference thereto.

In the skid control system of the aforementioned patent, the rear brakes were provided with a brake pres sure modulator for relieving the pressure delivered to the brakes upon detection of an incipient skid condition. In order to prevent deterioration of the valve from inaction, a system was provided for cycling the valve. The system further includes means for checking the operation of the valve during cycling to determine whether any malfunction in valve operation exists. As taught by the patent to Fielek, Jr., et al. the valve may be cycled. upon actuation of the ignition switch.

In most four wheel skid control systems, at least two modulating valves are used which together control the braking pressure at all of the braked wheels. Under some conditions, for example, when the vehicle is being held on a grade by application of the brakes by the vehicle operator, it is undesirable to allow the pressure delivered to all the brakes of the vehicle to be relieved simultaneously during a modulating valve check cycle. The present invention provides the means for normally cycling and checking all of the modulating valves of a plural valve anti-skid system, and yet, simultaneous relief of the brake pressure delivered to all of the brakes of the vehicle is inhibited if the brakes are actuated by the vehicle operator. This is accomplished by providing acycling inhibit circuit so that at least one valve is not opened to relieve brake pressure during an indication of brake actuation for example, as received from the brake light switch. Cycling of either the front modulating valve, the rear modulating valve, or both may be inhibited upon application of the brakes.

A BRIEF DESCRIPTION OF THE DRAWING The drawing is a diagram of an exemplary skid control system having a valve cycling control according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT URE, the front wheels are equipped with brake drums 1 0 and brake cylinders 12, and the rear wheels are equipped with brake drums l4 and brake cylinders 16.

The front wheel brake cylinders 12 are supplied with hydraulic pressure by a hydraulic line 18 which receives hydraulic pressure from a master cylinder 20 for the vehicle through a line 22. A front brake pressure modulating valve 24 is interposed in the front brake line 22 to control the fluid pressure to the front brake cylinders 12 in accordance with a skid control signal.

The rear brake cylinders 16 are supplied with hydraulic pressure by a fluid line 26 which receives hydraulic pressure from the master cylinder 20 through a fluid line 28. A rear brake modulating valve 30 is interposed in rear brake line 28 to control the fluid pressure to the rear brake in accordance with a skid control signal.

The front brake modulating valve 24 receives a skid control signal on a line 32 from a front skid control module 34. The front skid control module 34 receives signals representative of the wheel speed of each of the front wheels on lines 36 and 38 from left front wheel speed sensor 40 and right front wheel speed sensor 42, respectively. The rear brake modulating valve 30 receives a skid control signal on a line 44 from a rear skid control module 46. The rear skid control module 46 receives wheel speed signals from left and right rear wheel speed sensors 48 and 50 on lines 52 and 54, respectively.

' With regard to the operation of each of the front and rear skid control modules 34 and 46, and each of the front and rear modulating valves 24 and 30, respectively, reference is made to the aforementioned patent to Fielek, Jr., et al. In the patent to Fielek, Jr., et a1, a description of a skid control showing'a skid control module and modulating valve for the rear brakes is disclosed. It will be appreciated that the front brake skid control module 34 and front brake modulating valve 24 may be essentially duplicative of the skid control module and the modulating valve for the rear brakes as described in the aforementioned patentto Fielek, Jr., et al.

The front modulating valve 24 receives a cycling control signal from a front valve cycling and checking circuit 56 on line 58 while the rear modulating valve 30 receives a cycling control signal from a rear valve cycling and checking circuit 60 on line 62. The valve cycling and checking circuits 56 and 60 may be like the .valve cycling and checking circuit disclosed in detail in the aforementioned patent to Fielek, Jr., et al. However, in the present invention, the valve cycling and checking circuits 56 and 60 are not connected directly to the ignition switch '64 of the vehicle as disclosed in the above patent to Fielek, Jr., et al. Rather, a brake cycling inhibit circuit 66 is interposed between the valve cycling and checking circuits 56 and 60 and ignition switch 64. More specifically, the brake cycling inhibit circuit 66 is connected to the ignition switch 64 by a line 68 to receive a signal indicating actuation of the ignition switch and to the front and rear valve cycling and checking circuits 56 and 60 by lines 70 and 71, respectively. The brake cycling inhibit circuit is connected to the brake light switch 72 of the vehicle by a line 74. The brake cycling inhibit circuit 66 may be a transistor, relay or other switch which is opened responsive to a signal on line 74 consequent closing of the that the vehicle can be held on a grade. It should be understood that only one of the rear cycling and checking circuits 60 and the front cycling and checking circuit 56 may be inhibited rather than both, to achieve the objects of this invention.

The valve cycling and checking circuits 56 and 60, as described in the above patent to Fielek, Jr., et al, are operative to cause the diaphragm and piston assembly of the associated modulating valve 24 or 30 to move to their extreme, actuated position, and thereafter, to return to their deactuated position. Such motion is beneficial in maintaining the seals and valves of the modulating valves 24 and 30 in an operative condition. Each of the cycling and checking circuits 56 and 60, in addition to valve cycling, provides an indication of the proper functioning of the associated modulating valve 24 or 30, as also described in the aforementioned Fielek, Jr et al patent.

In view of the above, it will be appreciated that both of the front and rear modulating valves 24 and 30, respectively,'are not cycled simultaneously when the operator actuates the brakes. Consequently, actuation of the ignition switch 64 does not cause the brakes of the vehicles to be released so that the vehicle may be held on a grade by application of the brakes by the vehicle operator. Without means for preventing relief of the braking pressure to all of the brakes when braking pressure is needed, the vehicle would be allowed toroll, possibly with harmful results, and certainly in a disturbing manner.

I claim:

l. A skid control system for a wheeled vehicle comprising: a plurality of fluid control valves controllably actuable in response to a skid control signal for controlling the pressure to the brakes of the wheels of the vehicle, actuating means automatically actuable by the vehicle operator in operating the vehicle, valve cycling means connected to the actuating means of the vehicle and being actuated in response to actuation of the actuating means for cycling the valves without the prior occurrence of the control signal whereby the valves will be cycled at determinable times in order to prevent deterioration of the valves from inaction, said valve cycling meansincluding means responsive to the actuation of the brakes of said vehicle by the vehicle operator for preventing simultaneous actuation of all of said valves during actuation of the brakes of said vehicle by the vehicle operator.

2. A skid control system according to claim 1 having two fluid control valves independently controllably actuated in response to separate skid control signals.

3. A skid control system according to claim 1 having a first fluid control valve for controlling the pressure to the brakes of the front wheels of the vehicle in response to a front skid control signal and a second fluid control valve for controlling the pressure to the brakes of the rear wheels of the vehicle in response to a rear skid control signal.

4. A skid control system according to claim 1 wherein said actuating means is the ignition switch of the vehicle.

5. A skid control system according to claim 1 wherein said valves have a determinable cycle of operation and further including valve checking means for sensing a Y deviation from said determinable cycle of operation of said valves during cycling thereof.

6. A skid control system according to claim 1 wherein each of ,said valves includes a movable memher and wherein said valve cycling means causes said movable member to move to an extreme actuated position for release of brake pressure to an associated brake and to return to a deactuated position for reapplication of brake pressure to said associated brake.

7. A skid control system according to claim 1 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of all of said valves during the actuation of the brakes of said vehicle by the vehicle operator.

8. A skid control system according to claim 1 wherein said means responsive to the actuation of the brakes of said vehicle prevents the actuation of fewer than all of said valves during actuation of the brakes of said vehicle by the vehicle operator.

9. A skid control system according to claim 1 wherein said means responsive to the actuation of the brakes of said vehicle prevents the actuation of all but one of said valves during actuation of the brakes of said vehicle by the vehicle operator.

10. A skid control system according to claim 1 having two fluid control valves independently controllably actuated in response to separate skid control signals and wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of both of said valves during the actuation of the brakes of said vehicle by the vehicle operator.

1 1. A skid control system according to claim 1 having two fluid control valves independently controllably actuated in response to separate skid control signals and wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of one of said valves during the actuation of the brakes of said vehicle by the vehicle operator.

12. A skid control system according to claim 1 wherein said vehicle has a brake light switch and wherein said means responsive to the actuation of the brakes of said vehicle is connected to said brake light switch to respond thereto.

13. A skid control system for a wheeled vehicle comprising: at least two fluid control valves independently controllably actuated in response to separate skid control signals having a determinable cycle of operation for controlling the pressure to respective ones of the brakes of the wheels of the vehicle, actuating means automatically actuable by the vehicle operator, valve cycling means connected to the actuating means of the vehicle and being actuated in response to actuation of the actuating means for cycling the valves without the prior occurrence of the control signal whereby the valves will be cycled at determinable times in order to prevent deterioration of the valves from inaction, said valve cycling means including means responsive to the actuation of the brakes of said vehicle by the vehicle operator for preventing simultaneous actuation of all of said valves during actuation of the brakes of said vehicle by the vehicle operator and valve checking means for sensing a deviation from said determinable cycle of operation of said valves during cyclingthereof.

14. A skid control system according to claim 13 having a first fluid control valve for controlling the pressure to the brakes of the front wheels of the vehicle in response to a front skid control signal and a second fluid control valve for controlling the pressure to the brakes of the rear wheels of the vehicle in response to a rear skid control signal.

15. A skid control system according to claim 14 wherein said actuating means is the ignition switch of the vehicle,

16. A skid control system according to claim wherein each of said valves includes a movable member and wherein said valve cycling means causes said movable member to move to an extreme actuated position for release of brake pressure to an associated brake and to return to a deactuated position for reapplication of brake pressure to said associated brake.

17. A skid control system according to claim 16 wherein said vehicle has a brake light switch and wherein said means responsive to the actuation of the brakes of said vehicle is connected to said brake light switch to respond thereto.

18. A skid control system according to claim 17 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of both of said valves during the actuation of the brakes of said vehicle by the vehicle operator.

19. A skid control system according to claim 17 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of one of said valves during the actuation of the brakes of said vehicle by the vehicle operator.

20. A skid control system for a wheeled vehicle comprising: at least two fluid control valves independently controllably actuated in response to separate skid con-, trol signals having a determinable cycle of operation for controlling the pressure to respective ones of the brakes of the wheels of the vehicle, actuating means automatically actuable by the vehicle operator, valve cycling means connected to the actuating means of the vehicle and being actuated in response to actuation of the actuating means for cycling the valves without the prior occurrence of the control signal whereby the valves will be cycled at determinable times in order to prevent deterioration of the valves from inaction, said valve cycling means including brake cycling inhibit means responsive to the actuation of the brakes of said vehicle by the vehicle operator for inhibiting actuation of at least one of said valves during actuation of the brakes of said vehicle by the vehicle operator and valve checking means for sensing a deviation from said determinable cycle of operation of said valves during cycling thereof.

21. A skid control system according to claim 20 having a first fluid control valve for controlling the pressure to the brakes of the front wheels of the vehicle in response to a front skid control signal and a second fluid control valve for controlling the pressure to the brakes-of the rear wheels of the vehicle in response to a rear skid control signal.

22. A skid control system according to claim 21 wherein said actuating means is the ignition switch of the vehicle.

23. A skid control system according to claim 22 I wherein each of said valves includes a movable memher and wherein said valve cycling means causes said movable member to move to an extreme actuated position for release of brake pressure to an associated brake and to return to a deactuated position for reapplication of brake pressure to said associated brake.

24. A skid control system according to claim 23 wherein said vehicle has a brake light switch and wherein said means responsive to the actuation of the brakes of said vehicle is connected to said brake light switch to respond thereto.

25. A skid control system according to claim 20 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of both of said valves during the actuation of the brakes of said vehicle by the vehicle operator.

26. A sk-id control system according to claim 20 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of one-of said valves during the actuation of the brakes of said vehicle by the vehicle operator. 

1. A skid control system for a wheeled vehicle comprising: a plurality of fluid control valves controllably actuable in response to a skid control signal for controlling the pressure to the brakes of the wheels of the vehicle, actuating means automatically actuable by the vehicle operator in operating the vehicle, valve cycling means connected to the actuating means of the vehicle and being actuated in response to actuation of the actuating means for cycling the valves without the prior occurrence of the control signal whereby the valves will be cycled at determinable times in order to prevent deterioration of the valves from inaction, said valve cycling means including means responsive to the actuation of the brakes of said vehicle by the vehicle operator for preventing simultaneous actuation of all of said valves during actuation of the brakes of said vehicle by the vehicle operator.
 2. A skid control system according to claim 1 having two fluid control valves independently controllably actuated in response to separate skid control signals.
 3. A skid control system according to claim 1 having a first fluid control valve for controlling the pressure to the brakes of the front wheels of the vehicle in response to a front skid control signal and a second fluid control valve for controlling the pressure to the brakes of the rear wheels of the vehicle in response to a rear skid control signal.
 4. A skid control system according to claim 1 wherein said actuating means is the ignition switch of the vehicle.
 5. A skid control system according to claim 1 wherein said valves have a determinable cycle of operation and further including valve checking means for sensing a deviation from said determinable cycle of operation of said valves during cycling thereof.
 6. A skid control system according to claim 1 wherein each of said valves includes a movable member and wherein said valve cycling means causes said movable member to move to an extreme actuated position for release of brake pressure to an associated brake and to return to a deactuated position for reapplication of brake pressure to said associated brake.
 7. A skid control system according to claim 1 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of all of said valves during the actuation of the brakes of said vehicle by the vehicle operator.
 8. A skid control system according to claim 1 wherein said means responsive to the actuation of the brakes of said vehicle prevents the actuation of fewer than all of said valves during actuation of the brakes of said vehicle by the vehicle operator.
 9. A skid control system according to claim 1 wherein said means responsive to the actuation of the brakes of said vEhicle prevents the actuation of all but one of said valves during actuation of the brakes of said vehicle by the vehicle operator.
 10. A skid control system according to claim 1 having two fluid control valves independently controllably actuated in response to separate skid control signals and wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of both of said valves during the actuation of the brakes of said vehicle by the vehicle operator.
 11. A skid control system according to claim 1 having two fluid control valves independently controllably actuated in response to separate skid control signals and wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of one of said valves during the actuation of the brakes of said vehicle by the vehicle operator.
 12. A skid control system according to claim 1 wherein said vehicle has a brake light switch and wherein said means responsive to the actuation of the brakes of said vehicle is connected to said brake light switch to respond thereto.
 13. A skid control system for a wheeled vehicle comprising: at least two fluid control valves independently controllably actuated in response to separate skid control signals having a determinable cycle of operation for controlling the pressure to respective ones of the brakes of the wheels of the vehicle, actuating means automatically actuable by the vehicle operator, valve cycling means connected to the actuating means of the vehicle and being actuated in response to actuation of the actuating means for cycling the valves without the prior occurrence of the control signal whereby the valves will be cycled at determinable times in order to prevent deterioration of the valves from inaction, said valve cycling means including means responsive to the actuation of the brakes of said vehicle by the vehicle operator for preventing simultaneous actuation of all of said valves during actuation of the brakes of said vehicle by the vehicle operator and valve checking means for sensing a deviation from said determinable cycle of operation of said valves during cycling thereof.
 14. A skid control system according to claim 13 having a first fluid control valve for controlling the pressure to the brakes of the front wheels of the vehicle in response to a front skid control signal and a second fluid control valve for controlling the pressure to the brakes of the rear wheels of the vehicle in response to a rear skid control signal.
 15. A skid control system according to claim 14 wherein said actuating means is the ignition switch of the vehicle.
 16. A skid control system according to claim 15 wherein each of said valves includes a movable member and wherein said valve cycling means causes said movable member to move to an extreme actuated position for release of brake pressure to an associated brake and to return to a deactuated position for reapplication of brake pressure to said associated brake.
 17. A skid control system according to claim 16 wherein said vehicle has a brake light switch and wherein said means responsive to the actuation of the brakes of said vehicle is connected to said brake light switch to respond thereto.
 18. A skid control system according to claim 17 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of both of said valves during the actuation of the brakes of said vehicle by the vehicle operator.
 19. A skid control system according to claim 17 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of one of said valves during the actuation of the brakes of said vehicle by the vehicle operator.
 20. A skid control system for a wheeled vehicle comprising: at least two fluid control valves independently controllably actuated in response to separate skid control signals having a determinable cycle of operation for controlling the pressure to respective ones of the brakes of tHe wheels of the vehicle, actuating means automatically actuable by the vehicle operator, valve cycling means connected to the actuating means of the vehicle and being actuated in response to actuation of the actuating means for cycling the valves without the prior occurrence of the control signal whereby the valves will be cycled at determinable times in order to prevent deterioration of the valves from inaction, said valve cycling means including brake cycling inhibit means responsive to the actuation of the brakes of said vehicle by the vehicle operator for inhibiting actuation of at least one of said valves during actuation of the brakes of said vehicle by the vehicle operator and valve checking means for sensing a deviation from said determinable cycle of operation of said valves during cycling thereof.
 21. A skid control system according to claim 20 having a first fluid control valve for controlling the pressure to the brakes of the front wheels of the vehicle in response to a front skid control signal and a second fluid control valve for controlling the pressure to the brakes of the rear wheels of the vehicle in response to a rear skid control signal.
 22. A skid control system according to claim 21 wherein said actuating means is the ignition switch of the vehicle.
 23. A skid control system according to claim 22 wherein each of said valves includes a movable member and wherein said valve cycling means causes said movable member to move to an extreme actuated position for release of brake pressure to an associated brake and to return to a deactuated position for reapplication of brake pressure to said associated brake.
 24. A skid control system according to claim 23 wherein said vehicle has a brake light switch and wherein said means responsive to the actuation of the brakes of said vehicle is connected to said brake light switch to respond thereto.
 25. A skid control system according to claim 20 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of both of said valves during the actuation of the brakes of said vehicle by the vehicle operator.
 26. A skid control system according to claim 20 wherein said means responsive to the actuation of the brakes of said vehicle prevents actuation of one of said valves during the actuation of the brakes of said vehicle by the vehicle operator. 